东洞庭湖流域抗生素抗性基因的时空分异特征及多介质传输机制

East Dongting Lake is an important hub to connect the Dongting Lake and the Yangtze river, and the water quality of East Dongting Lake is directly related to the ecological security of the National Nature Reserve and the South-to-North Water Diversion Project of Yangtze river. Due to the vast pollutants emission from breeding industry in the East Dongting Lake basin, antibiotics and antibiotic resistance genes (ARGs) problems are highlighted. On the base of the antibiotics pollution and the characteristics of the East Dongting Lake basin, researches have been made on the reserve, sources and transmission pattern of antibiotic resistance genes (ARGs) from the input and migration path of antibiotics in different seasons. Combining the field investigation, Environmental Fluid Dynamics (EFDC) model and the modified Gaussian diffusion model, the project will study the temporal and spatial distribution of antibiotic resistance genes (ARGs), clarify the responding relationship of ARGs pollution sources and the East Dongting Lake reserves, discuss the key mechanism and influence factors of aqueous phase - gas phase transmission, identify the key control areas and pollution factors of ARGs, then provide policy support for the environmental risk control of ARGs in East Dongting Lake basin, human health assessment and water quality security of the South-to-North Water Diversion Project of Yangtze river.

东洞庭湖是洞庭湖联通长江的枢纽，其水质的好坏关系到国家级自然保护区生态及长江的调水安全。东洞庭湖流域养殖业等抗生素使用量大，抗生素及抗性基因污染问题凸显。本项目基于东洞庭湖流域抗生素污染问题及流域特征，从抗生素抗性基因的输入与迁移路径上分季节开展抗生素抗性基因的赋存、来源和传输规律的研究，通过将野外调查与环境流体动力学模型（EFDC模型）、修正的高斯模型相结合，明确抗生素抗性基因的时空分异特征，厘清抗性基因污染来源与湖区赋存的响应关系，揭示水相与气相传输的关键机制和影响因子，确定抗生素抗性基因的重点管控区及管控因子，进而为东洞庭湖流域抗性基因的环境风险控制、人体健康评价及长江的调水安全保障提供决策支持。

本项目以长江重要通江湖泊洞庭湖中的东洞庭湖为研究对象，采集了东洞庭湖湖区、入湖口、入江口、自然保护区的核心区等区域表层水、沉积物和大气干湿沉降等样品，分析了东洞庭湖水环境中抗生素及抗生素抗性基因（ARGs）的时空分异特征，厘清了陆源与大气源（干/湿沉降）抗生素抗性基因的时空分异特征及入湖通量，并对东洞庭湖水环境中水体状态进行模拟以解释抗生素抗性基因的传输机制。取得的主要研究成果如下：.（1）东洞庭表层水中的抗生素浓度呈现春季>秋季>夏季的季节规律，沉积物中呈现秋季>夏季>春季。氧氟沙星与磺胺甲恶唑为东洞庭湖主要污染抗生素种类，表现出高环境风险，空间分布上在靠近人类活动频繁区域和水产养殖区的点位，抗生素污染最为严重。东洞庭湖流域表层水中优势ARGs是sul1和sul2，季节变化上，表层水表现为夏季＞春季＞秋季，沉积物表现为春季＞秋季＞夏季。空间分布上，ARGs总丰度表现为上游＞下游。.（2）东洞庭湖及滨湖区的陆地污染源中，畜禽养殖区和水产养殖区都受到磺胺类和四环素类ARGs的普遍污染，污水处理厂是ARGs向水环境中传播的主要途径，污水处理厂入湖通量介于1.45×1014~4.22×1017 copies/a，sul1、sul2和int1是污水处理厂向东洞庭湖输入的主要污染ARGs。.（3）东洞庭湖及滨湖区大气总沉降中，ARGs绝对丰度范围为0~3.90×106 copies/mL，ARGs绝对丰度呈畜禽养殖区>人口密集区>水产养殖区空间分布特征。sul1、int1和qnrS是夏季湿沉降中的主要基因型，int1、sul2和tetM是秋季湿沉降中的主要基因型，大气沉降通量介于0~1.18×1010 copies/(m2•月)之间。.（4）应用EFDC模型对水体流态、抗生素和抗生素抗性基因传输过程进行了模拟。结果显示东洞庭湖抗生素污染季节分布呈波动变化趋势，夏秋季节污染较重。空间上呈“自东向西”传输规律，在东洞庭湖西半部分抗生素存在蓄积现象，ARGs模拟结果显示其在西半部分湖区的绝对丰度高于其他区域，东半部分消散较快。